package JavaStructure.LinkedList;


public class MyLinkedList {

    static class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }

    //标记头
    public ListNode head;
    //标记尾
    public ListNode last;

    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        if(head == null) {
            head = node;
            last = node;
        }else {
            node.next = head;
            head.prev = node;
            head = node;
        }
    }
    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if(head == null) {
            head = node;
            last = node;
        }else {
            last.next = node;
            node.prev = last;
            last = node;
        }
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        int size = size();
        if(index < 0 || index > size) {
            System.out.println("下标位置不合法："+index);
            return;
        }
        if(index == 0) {
            addFirst(data);
            return;
        }
        if(index == size) {
            addLast(data);
            return;
        }
        ListNode node = new ListNode(data);
        ListNode cur = search(index);
        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;
    }

    private ListNode search(int index) {
        ListNode cur = head;
        while (index != 0) {
            cur = cur.next;
            index--;
        }
        return cur;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    //删除头节点
                    head = head.next;
                    if(head == null) {
                        //只有一个节点的情况下
                        last = null;
                    }else {
                        head.prev = null;
                    }
                }else {
                    //删除中间和尾巴
                    if(cur.next == null) {
                        //尾巴
                        cur.prev.next = cur.next;
                        last = last.prev;
                    }else {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    }
                }
                return;
            }
            cur = cur.next;
        }
    }

    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    //删除头节点
                    head = head.next;
                    if(head == null) {
                        //只有一个节点的情况下
                        last = null;
                    }else {
                        head.prev = null;
                    }
                }else {
                    //删除中间和尾巴
                    if(cur.next == null) {
                        //尾巴
                        cur.prev.next = cur.next;
                        last = last.prev;
                    }else {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    }
                }
                //return;
            }
            cur = cur.next;
        }
    }

    //得到单链表的长度
    public int size(){
        ListNode cur = head;
        int count = 0;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }
    public static void display(ListNode head){
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }

    public void display(){
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }

    public void clear(){
        ListNode cur = head;
        while (cur != null) {
            ListNode curN = cur.next;
            //cur.val = null;
            cur.prev = null;
            cur.next = null;
            cur = curN;
        }
        head = null;
        last = null;
    }

    //分割列表：
    // 给你一个链表的头节点 head 和一个特定值 x ，请你对链表进行分隔，使得所有 小于 x 的节点都出现在 大于或等于 x 的节点之前。
    public  ListNode Solution(ListNode head,int key){
    //直接尾插不行：找不到尾在哪，会增加遍历
//        ListNode cur = head.next;
//        ListNode curX = head;
//
//        while (cur != null) {
//            if(cur.val >= key) {
//                cur = cur.next;
//
//            }
//        }
        ListNode as = null;
        ListNode ae = null;
        ListNode bs = null;
        ListNode be = null;

        ListNode cur = head;
        //分拣法：“没有尾巴就创造几个篮子，这下有尾巴啦”
        while (cur != null){
            if(cur.val < key){
                if(as == null){
                    as = cur;
                    ae = cur;
                }else{
                    as.next = cur;
                    as = as.next;
                }
            }else{
                if(be == null){
                    bs = be = cur;
                }else{
                    bs.next = cur;
                    bs = bs.next;
                }
            }

            cur = cur.next;

        }

//        if(ae == null){
//            return be;
//        }
//        as.next = be;
//
//        if (bs != null) {
//            be.next = null;
//        }
//        return ae;
//    }

    if(ae == null){
        return be;
    }

    // 在你前面的遍历中，be只有第一次为null的时候，才会进行复制，其余时间都是bs 在往后进行移动，所以本质上，be被你当作了链表的头部，bs是尾部
        // 所以在打印之前，应该将be链表的尾部置为null，就不会因为原本链表的值影响打印
    if (be != null) {
        bs.next = null;
    }

    MyLinkedList.display(ae);
    MyLinkedList.display(be);

    // 链表： 1 4 3 2 5 2
    // 如果放在这个位置，此时你的bs是指向的是5，5后面得 已经放在ae这个链表上了，你没有将5 的next置为null，那么你上面打印be这个链表的时候，2 就会被打印出来
//    if (be != null) {
//        bs.next = null;
//    }

    as.next = be;


    return ae;
    }
}


